1. Field of the Invention
The present invention relates to a process for testing a data transmission system by which data are transmitted across two data transmission links and across a first transmission device and a second transmission device, in which, in dependence upon a loop signal, a test loop is closed and a transmission section is tested.
2. Description of the Prior Art
In order to test a data transmission system in which data are transmitted by way of two lines across two transmission devices in both directions, a loop signal in the region of the first transmission device could be used to close a test loop so that, on the one hand, the loop signal outgoing from the second transmission device and, on the other hand, the loop signal returned by way of the test loop and the first transmission device, are available in the region of the second transmission device for remote analysis.
It is basically conceivable for the test loops assigned to the individual transmission devices to be controlled by different loop signals so that the return of individual loop signals does not result in the closure of other test loops and does not result in an intercept state in which a loop signal constantly circulates between two transmission devices, and in this manner prevents intended data transmission. Differing loop signals of this kind necessitates a relatively high technical and organizational expense for the production and analysis of the loop signals, so that it appears expedient to operate two transmission devices with the same loop signals, the same loop signal recognition stages and the same fault analysis stages. However, under these conditions, intercept states can occur in which closed line systems, which prevent regular data transmission for an unlimited period of time, form between two transmission devices.